In recent years, a storage apparatus employing a virtualization technology has been provided. The virtualization technology as herein referred to is a technology for virtualizing a plurality of physical storage devices included in the storage apparatus and presenting the plurality of physical storage devices as a single storage device to a host computer.
The following Non Patent Literature 1 describes an approach in which a user periodically researches an area which can be released by an application, and if the area which can be released is found, the storage apparatus is notified of it. When the storage apparatus recognizes a reusable area from the notification, the storage apparatus collects and reuses the area.